Keyword searching techniques are used in a wide variety of applications. For example, in some applications, communication traffic is analyzed in an attempt to detect keywords that indicate traffic of interest. Some data security systems attempt to detect information that leaks from an organization network by detecting keywords in outgoing traffic. Intrusion detection systems sometimes identify illegitimate intrusion attempts by detecting keywords in traffic.
Various string matching techniques are described, for example, by Navarro and Raffinot, in “Flexible Pattern Matching in Strings—Practical On-Line Search Algorithms for Texts and Biological Sequences,” Cambridge University Press, 2002, which is incorporated herein by reference. Chapter 2 of this book reviews string matching algorithms such as Knuth-Morris-Pratt (KMP), Boyer-Moore, Horspool, Backward Non-deterministic Dawg Matching (BNDM) and Backward Oracle Matching (BOM).